Rectifier



June 19, 1934. E. A. E. TORNBLOM RECTIFIER Filed May 25, 1932 4 Sheets-Sheet l June 19, 1934.

E. A. E. TORNBLOM RECTIFIER Filed May 25. 1932 4 Sheets-Sheet 2 June 19, 1934. E. A. E. TORNBLOM RECTIFIER Filed May 25, 1932 4 Sheets-Sheet 3 7 1! ai 'af w l n 1934- E. A. E. TORNBLOM RECTIFIER Filed May 26, 1932 4 Sheets-Sheet 4 Patented June 19, 1934 UNITED STATES PATENT OFFICE RECTIFIER Application May 26, 1932, Serial No. 613,733 In Sweden March 23, 1932 17 Claims.

This invention relates to rectifiers adapted to rectify alternating electric currents to direct currents. To be a little more specific the invention relates to a rectifier of the kind having a field rotating synchronously with the frequency of the alternating current and adapted to drive a contact body at a synchronous speed, the said contact body cooperating, in working position, with commutating means connected with the phases of the alternating current. In apparatus of the kind referred to it has been customary to provide a special starting motor adapted to start the contact body and to accelerate the mass of the body to a speed synchronous with the rotary field. Only at the moment when the mass of the contact body reaches full synchronous speed the rotary field itself will be able to drive the body and to maintain its speed at the synchronous value, so that the starting motor may be switched off. The primary object of the invention is to avoid the necessity of such starting motor and for this purpose I provide means for guiding the contact body during the starting period to cause the said body to move successively from a central position of rest to a position in which the body engages the commutating means. By the aid of said guiding means and under the influence of the rotary field the contact body is caused to roll during the starting period on a helical line, initiating at the central position of the contact body and terminating at the position engaging with the commutators. Under such conditions the rotary field itself can start the contact body from the position of rest in which the radius of the path of the rolling movement of the contact body is zero or near zero, the radius then increasing successively to a predetermined value in the position engaging the commutators and consequently the necessary energy for overcoming the inertia of the mass of the contact body in its position of rest is sufficiently reduced to enable the rotary field to drive the said mass at a synchronous speed already in the starting moment without using any auxiliary starting motor. The contact body is then guided successively in a helical path towards its commutating position.

Further objects and advantages of the inven- 0 tion will be described with reference to the accompanying drawings which illustrate the invention in some preferred embodiments and in which Figure 1 represents a diagrammatical view of a rectifier embodying my invention,

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Figure 2 a preferred embodiment of a magnet suitable for use in the apparatus,

Figures 3 and 4 horizontal and vertical sections respectively of a constructional form of a contact apparatus forming part of the rectifier,

Figure 5 a vertical section of a modified construction,

Figure 6 a general view showing a complete equipment with a transformer and a contact apparatus and Figure '7 a schematic diagram of connections of the embodiment shown in Figure 1.

With reference to the diagrammatical embodiment illustrated in Figures 1 and '7 the rectifier substantially comprises two parts, namely an alternating current transformer A and a contact apparatus B electricallyconnected therewith. The transformer A may be a two-phase or a poly-phase transformer adapted to convert the incoming alternating current to a rotating cur- 7 rent and also to transform the voltage of the alternating current to a higher or lower value if necessary. In the embodiment shown in the drawings the transformer A consists of a cylinv drical iron core, preferably made by a great number of circular plates or sheets, which are associated to form a cylindrical core stacking. About half-way between the periphery and the centre of the cylinder I provide borings 10 adapted to receive the transformer windings. The primary or the alternating current windings (shown in Fig. 7 at may be similar to the stator winding of an induction motor for the voltage and type of current to be rectified. Also the secondary windings, indicated at 11, are arranged 90 in the borings 10 but are electrically insulated from the primary and may be connected similar to the armature coils of a two-pole direct current motor of the wellknown type. The windings 11 are provided with points of connection 12-19, the number of which corresponds to the number of the commutator segments of the contact apparatus B. If the secondary windings comprise several windings, they may be connected in series or in parallel.

In operation, alternating current is supplied to to primary 90 of the transformer thereby producing in the secondary winding 11 a multi-phase current, rotating at a speed corresponding to the frequency of the primary alternating current. Assuming that the primary current has a frequency of 50 periods per second the multi-phase current in the secondary winding 11 will rotate at a speed of 3000 revolutions per minute. It will be obvious that if a pair of sliding contacts cooperating with the points 12-19 are caused to rotate synchronously with the said multi-phase current, a pure direct Cllll3lll) may be delivered from the sliding contacts. I will also be obvious that the highest potential difference of the multi-phase current is establishe between two diametrically opposite points of winding 11, say between points -2 16, 13 and 17 etc.

In order to accomplish the synchronous movement of tr e contacts practically I provide the contact apparatus B comprising a frame c rrying two pairs of fixed electro-magnets 21, 23 and 22, 24 respectively, the magnets of each pair being arranged diametrically one opposite the other. The ma nets are p ovided with diagrammatically indicated windings or coils 21 22 23 24 and current is supplied to each pair of the coils 21 23 and 22 24 from a pair of diametrically opposite points of the secondary 11, said pairs of points being displaced one from the other at an angular distance of 90. By way of example, the points 14 and 18 may supply current to coils 21 and 23, whilst po its 12 and 16 may supply current to coils and (Figure 7). The connecting wires extending from the selected points of the secondary 11 to the field coils of the contact apparatus re not shown in Figure l but for sake of simplicity the connecting terminals 12 16 14 18 of the field coils 2 2-, 22, 21, 23 in this figure are designated in such way that he proper connections are obtained by connecting the said terminals h tho points of the secondary designated wcorraponding reference numerals (12, 16 and l4, 18 respectively). As shown in Figures 1 and 7 each pair 21 23 and 22 24 of the field coils are also associated by means of conductors, connecting the coils so as to provide opposite magnetic poles at the upper ends or" the magnets in each system 21, 23 and 22, 24 respectively, i. e. if magnet 21 has positive pole, magnet 23 has negative pole at the upper ends.

The contact body of the contact apparatus comprises a. polarized armature and one or several contact rollers engaging with suitable commutators. The armature 25 which is arranged in the space between magnets 21. 22, 23 and 24 is surrounded by a stationary solenoid 26 preferably fixed to the frame 20. The connecting terminals 2'7, 28 of the solenoid 26 are supplied with direct current, which in starting the rectifier may be delivered from a battery or another external source of energy and during the working of the rectifier the direct current may be supplied from the current rectified by the rectifier. By the influence of the flux from the solenoid 26 the armature 25 obtains a determined and constant magnetic polarity. The armature is attached to a shaft 29 carrying two contact rollers 30, 31, which are rotatably mounted on the shaft but electrically insulated therefrom. Ihe rollers 30, 31 are provided with conical extensions 32, 33 tapering downwardly and surrounded by seats 34, "35, which have conical inner surfaces and are formed in brackets on the frame 20.

The contact rollers 30, 31 are adapted to roll in the inner contact surfaces of the commutators 36, 37, att ched to the frame 20 and comprising eight segments 12 19 which are obliquely arranged and insulated from one another. By conductors (shown in igure '7) each segment is connected with a selected one of the points 12-l9 of the transformer A, segment 12 being connected to point 12, segment 13 being connected to point 13 etc. As will be apparent from selected points of the said s condary.

the drawings each segment of the upper commutator 36 is connected with the same point of the secondary winding 11 of the transformer as the diametrically opposite segment of the lower commutator 37. In other words, the upper and lower segmennts are displaced an angle of 180 in relation to one another.

In the position of rest f the apparatus the conical extensions 32, 33 engage the conical seats 34 and 35 and in this position the centre of the armature 25 preferably is situated below a horiaontal plane through the centres of the magnets 21--2-i. The solenoid 25 is provided with a spacious centre bore enabling the armature 25 to move freely within determined limits. A corresponding air gap is provided between the inner contact surfaces of the commutators 36, 37 and the contact rollers 30, 31.

In starting the apparatus, alternating current is supplied to the primary of the transformer A and as a result or" the induction produced in the iron core by alternating current, a multiphase current is generated in the secondary winding 11. From the points 12--l9 the multi-phase current supp ed to the corresponding connect-- ing terminals l2 l8 of the field coils and to seg-nents 12 19 of the commutators 36 and 37. At t-.e same time direct current is supplied irom any source of energy to terminals 27, 23 of the solenoid 26. The multi-phase current supplied to field coils 2l2 i from transformer otary field which will tend to move .5 polarized by the flux of the solenoid 26. Since the centre of the armature lies below the centres of the magnets, the armature will try to r'se simultaneously as its centre of gravity, under 19 action of the rotary field, has

the tendency to move in a circular path at a speed which is synchronous with the velocity of the multi-phase current, for instance cc revolutions per minute. As a result of the raising and circular movement the conical extensions 32, 33 are caused to roll in the inner conical surfaces of the seats 34, 35. The pressure against the said conical surfaces produces a vertical component of force, which raises armature 25 further so that the armature guided by the conical suraces 34, is permitted to move on a path having a successively increasing radius. It will be obvious that the centre of gravity of the armature will thus be driven by the rotary field synchronously in helical path the radius of which increases successively from zero to a predetermined value and at the same time the armature is raised wider the action of the vertical component of the cone pressure and the vertical field component acting in the same direction. When the radius of the path of movement of the ar ature 25 reaches a sufiicient length the contact rollers 30, 31 engage the in of the transformer A, and at the same time en- I gaging the segments 12' -'i9- with Since the rollers in operative position, engage the tators and rotate synchronously with the current connected in the secondary 11 and since this current is supplied to the commutators a pure direct current can be collected at the current collectors 38, 39. It should be remembered that the polarity of the upper collector 38 is always opposite to the polarity of the lower collector 39, owing to the fact that each segment of the upper commutator 36 is displaced 130 to the corresponding segment of the lower commutator 37.

By reason of the comparatively heavy pressure between the contact rollers and the contact surfaces of the commutators, the commutation will be effected substantially sparkless even at considerable currents, and, at the same time, the wear of the segments is reduced to a minimum, since the engagement with the contact rollers is effected by means of rolling friction and not by sliding friction. The mechanical loss of the apparatus is very low as the armature has no mechanical support in operative position but is carried by the vertical components of the field and the cone pressure exclusively. These features of the improved rectifier result in a very high efiiciency in relation to known types of rectifiers. A

further advantage is that the size of the apparatus may be reduced.

In order to prevent an unintended engagement of the conical extensions 32, 33 with the edges of the seats when the conical extensions 32, 33 have been raised from the conical seats 34, 35, I prefer to construct the magnets so as to cause the top of the axis of the armature to incline in an opposite direction to the rolling direction of the con tact rollers.

Figure 2 illustrates an especial form of the magnets 2124 to accomplish this result. As shown in the drawings illustrating a magnet in perspective view, the upper right corner 40 of the laminated pole piece is cut away so that the field will be weaker at this edge than at the left edge 41. This deformation of the field causes the upper end of the armature to lag somewhat behind the lower end, provided that the armature rolls in a clockwise direction. In other words, the top of the axis of the armature is caused to incline towards the left. By the reason of this inclined position the tendency of the conical extensions to engage with the edges of the conical seats is avoided. If the rolling direction of the armature is chosen to be effected in a counter-clockwise direction,

the upper left corner of the pole piece is cut away to cause the axis to incline towards the rolling direction.

Figure 2 also illustrates that oblique equal large portions are cut away from the lower edges 42, 43 of the pole piece, the upper corner of the right edge 42 and the lower corner of the left edge 42 being removed. This assymetrical form of the pole piece enables the armature to occupy a substantially fixed elevational position during the working of the apparatus, so that the armature is prevented to be raised too much. By bevelling the corners as described the resulting acting line of the field will be situated about at 44 so that the centre of gravity of the armature tends to take up a fixed position to this line, thereby preventing a raising motion over a determined level.

A constructional embodiment of the contact apparatus is shown in Figures 3 and 4, the former being a horizontal section of the contact apparatus, whilst Figure 4 is a vertical section along the lines IVIV of Figure 3.

The contact apparatus comprises two covers 45, 46 associated together by means of bolts 4'7 to form a rigid support for the construction. At-

tached by screws 49 to the peripheral part of the covers 45, 46 are the laminated magnets 21, 22, 23, 24, which are surrounded by coils 21 22, 23 24 having a suitable number of turns depending upon the voltage used. In the centre of the covers 45, 46 are recesses 51 adapted to receive funnel-like or conical seats or rings 34 and 35. Above seat 34 and beneath seat 35, segment commutators 36 and 37 respectively are provided having conical inner contact surfaces and attached to cylindrical members 54, fixed to the covers 45, 46 by means of bolts 55. Insulating collars 56 are interposed between the members 54 and the 'commutators 36 and 37.

Arranged in the space between the four magnets is an armature 25 which is surrounded by a solenoid 26 rigidly associated with the cover 46 by means of supports 59. As will be apparent from the drawing a horizontal plane assumed to pass through the centre of the solenoid and the magnets lies above a horizontal plane passing through the centre of the armature 25. The armature 25 is fixed to a shaft 29 on which two tubular contact rollers 61 are rotatably mounted but electrically insulated from the shaft by means of insulating members 62. The rollers have conical extensions 32 and 33, the taper of which substantially corresponds to that of the conical seats 52.

The electrical connection of the apparatus and the general construction of the transformer (not shown) is similar to that described with reference to Figures 1 and '7. The necessary joints of connection are effected on the panels 64. The direct current is collected from the contact rollers 61 by means of collectors 6'7 carried by rods 65, which are insulated from the support at 66 and which are connected to the supply net works.

The operation of the apparatus is substantially the same as described with reference to Figure 1. Under the action of magnetic and mechanical forces the armature is lifted in a helical path in the conical seats till the radius of the circular movement of the armature increases sufficiently to enable the contact rollers 61 to engage the commutators 36 and 37. By constructing the magnets as described with reference to Figure 2 the tendency of the extensions 32 and 33 to engage with the surfaces of the seats 34 and 35 under working conditions is avoided and the armature is prevented from rising above a determined level.

To enable the current to be collected from the contact rollers 61 without preventing the free raising movement of the armature in the startin moment the rods 65 of the collectors 67 are resilient and the collectors are adapted and arranged so as to slide against the inner walls of the tubular contact rollers after starting the contact body.

Figure 5 illustrates a vertical section of a further embodiment of the contact apparatus, in which the conical seats are movable. It will be understood that if the seats are lowered in relation to the conical extensions during the starting period, the armature will be permitted to move in a helical path in the horizontal plane without any tendency to rise. The same result may be obtained by arranging the seats displaceably in relation to one another.

It will be noted that this arrangement ensures the armature to occupy a fixed elevational position at all times, so that the collecting of the current is facilitated.

In Fi ure 5 the same reference characters refer to similar parts as in Figures 3 and 4. The electrical connections and the principal operation is similar to that oi the apparatus shown in Fi 1.

The conical movable seats 34, are attached to bolts 68 extending upwardly at '70 and associated by means of the transverse member 69. The movement of the seats is guided by the fixed guides 71, provide' with slots '7? in which the seats are mounted to slide vertically. The dotted lines '73 indi ate the lowest position of the lower seat 35, whilst the full lines indicate the upper position of the seats. The current collectors being fixed to the contact rollers 51 provided with spr g means and are adapted to serve as supports ior inaiifaining the armature in a fixed horizontal position. The remain ing of the contact apparatus are constructed similar to ""3 parts shown in S-r'ires 3 and l.

The cporatof the apparatus i he following. The enei 1g of the magn. by multiphase current cm the transfo er A (Figure 1) produces a rotary field ten g to move the polarized armature which, how ver, is 1 vented from following tl is movement by .e seats 34, 35 in which the conical extensions 32, 33 of th armature rest. If the seats now are lowered by pr ssing the transverse member 69 downwardly the armature is released and is perniitted to roll in a helical horizon l path the radius of which increases success accord in as the seats are lowered. Wh n lowered in a sufiicient degree th l engage the inner surfaces 36, 37 in which they continue nously with the speed of field. seat-s 35 are lowers further to avoid any risk of engagement of the conical parts 32, 33

ithe seats resulting in sparking commutaconical Preferably the lowering movement of the seats s 35 is effected positively simultaneously with sup ly of cur t to the apparatus. illustrating s. cc ice for this purpose shows a oinplete equipment wi i th transformer A and be contact apparatus By levers 79, 80, 81 1e transverse member =39 shown in Figure 5 is ociated with the handle '78 of the starting tch or the starter '7'? of the apparatus. By eons of a slot 82 in lever 81 the handle '78 is ermit-ted to move within :ertain limits without fiecting said lever. T iereicre when he handle 8 f t: e starter T! is moved to switch on ourthe contact knives of the switch are perto engage the contacts without moving i ver 81. (July after the knives having contact position thereby switching Figure by means of the transverse member 69 and the bolts 68, thus releasing the armature, which is now free to start its movement in the h lical horizontal path.

The elevational position of the armature is maintained at a constant level by the resilient current collectors '74, '75.

In stopping the apparatus the seats 34, 2-5 are raised by the levers 79, 80, S1 and the handle '78 before current is interrupted, so that the armature is ready to occupy its position of rest in the seats as soon as current is switched off. Instead of connecting the seats 34, 35 with the switch 77 mechanically electro-magnetic device may be used for raising and lowering the seats. The circuit of the said device preferably neeasvc is controlled by the starter 7'7 of the apparatus.

The conical seats 34, 35 also may be displaced in relation to one another for the purpose described but in this event the smallest or the widest end respectively of one cone should be directed towards the smallest or widest end of the other cone. Furthermore, the seats can be mounted on a support actuated by spring means, which are compressed by the movement of the armature, causing a lowering movement of the seats.

The armature may have any desirable form and may consist of a permanent magnet instead of being polarized by a solenoid. The contact apparatus also may be arranged so as to permit the axis of the armature to occupy a horizontal position if desired. In this case the necessary aressure for the enga ement with the conical ,eats is exerted by the resilient spring actuated collectors.

While a specific embodiment of the invention illustrated and described it to be understood that alterations of 51s dei lie or" conruction may be made without departing from the spirit of the invention.

Having now fully described my invention, what new and desa'e to protect by Letters 1. In a rectifier commi' ting means, a contact body, means producing a rotary field, which drives the contact body at a synchronous speed and means for guiding the contact body during the s g period to cause the said body to move in a helical path to the position where the contact body engages with the commutating means.

2. In it recti er commutating means, a contact body, means producing a rotary field, which drives the contact body at synchronous speed, conical parts associated with the contact body and conical seats adapted to cooperate with the said conical parts to guide the contact body in a helical path during the starting period.

3. In a rectifier comnutating means, a contact body, means producing a rotary field, which dl'iVuS the coi...act body at a synchronous speed, conical parts associated with the contact body ceable conical seats adapted to cooperate wlth the said conical parts to guide the contact body in a helical path during the starting period.

4. In a rectifier commutating means, a contact body, means producing a rotary field, which drives the contact body at a synchronous speed, conical parts associated with the contact body, displaceable conical seats adapted to cooperate with the said conical parts to guide the contact body in a helical path during the starting period, a starting switch, and a coupling mechanically connecting a bovable part of the switch with the displaceable seats.

5. In a rectifier commutating means, a contact body, means produ rotary field, which drives the contact body at a synchronous speed, conical parts associated with the contact body, displaceable conical adapted to cooperate with the said conical parts to guide the contact body in a helical path during the starting period, a starting switch, and a coupling mechanically connecting the handle of the switch with the displaceable seats and adapted to permit loose motion within determined limits between the handle of the switch and the coupling.

6. In a rectifier commutating means, a contact body, means producing a rotary field, which drives the Contact body at a synchronous speed, conical parts associated with the contact body, displaceable conical seats adapted to cooperate with the said conical parts to guide the contact body in a helical path during the starting period and an electromagnetic device operating the said conical seats.

7. In a rectifier commutating means, a contact body, means producing a rotary field, which drives the contact body at a synchronous speed, conical parts associated with the contact body, displaceable conical seats adapted to cooperate with the said conical parts to guide the contact body in a helical path during the starting period and spring means adapted to support the displaceable seats.

8. In a rectifier two commutators having a number of segments, means connecting each segment of one commutator with a segment of the other commutator, a contact body, means producing a rotary field which drives the contact body at a synchronous speed and which rotates synchronously with the frequency of the alternating current to be rectified, and means for guiding the contact body during the starting period to cause the said body to move in a helical path to the position where the contact body engages with the segments.

9. In a rectifier two commutators having a number of segments, means connecting each segment of one commutator with a segment of the other commutator, a contact body, contact members mounted on the contact body, means producing a rotary field which drives the contact body at a synchronous speed, means for guiding the contact body during the starting period to cause the said body to move in a helical path to the position where the contact members engage with the segments and current collectors associated with the contact members.

10. In a rectifier commutating means, a contact body, tubular contact rollers rotatably .mounted on the contact body, means producing a rotary field, which drives the contact body at a synchronous speed, means for guiding the contact body during the starting period to cause the said body to move in a helical path to the position where the contact rollers engage with the commutating means and resilient current collectors adapted to cooperate with the inner walls of the tubular contact rollers.

11. In a rectifier commutating means, a contact body, contact rollers rotatably mounted on the contact body, means producing a rotary field, which drives the contact body at a synchronous speed, means for guiding the contact body during the starting period to cause the said body to move in a helical path to the position where the contact rollers engage with the commutating means, and current collectors rigidly fixed to the rollers and adapted to cooperate with the rollers.

12. In a rectifier commutating means, a polarized armature, contact members associated with the armature, means producing a rotary field, which drives the armature at a synchronous speed, and means for guiding the armature during the starting period to cause the armature to move in a helical path to the position where the contact members engage with the commutating means.

13. In a rectifier commutating means, a polar ized armature, contact members carried by the armature, means producing a rotary field which drives the armature at a synchronous speed, means for guiding the armature during the starting period to cause the armature to move in a helical path where the contact members engage with the commutating means and a solenoid adapted to polarize the armature and supplied With direct current.

14. In a rectifier commutating means, a polarized armature, contact members carried by the armature, electromagnets arranged around the armature, conductors supplying multiphase current to the magnets, and means for guiding the armature during the starting period to cause the armature to move in a helical path to the position where the contact members engage with the commutating means.

15. In a rectifier commutating means, a polarized armature, contact members carried by the armature, electromagnets arranged in such elevational position around the armature that in its position of rest a horizontal plane through the centres of the magnets lies below a horizontal plane through the centre of the armature and. means for guiding the armature during the starting period to cause the armature to move in a helical path to the position where the contact members engage with the commutating means.

16. In a rectifier commutating means, a polarized armature, contact members carried by the armature, electromagnets surrounding the armature and adapted to produce an assymetrical field to cause the top of the axis of the armature to incline towards the rolling direction of the armature, conductors supplying multi-phase current to the magnets, and means for guiding the armal ture during the starting period to cause the armature to move in a helical path to the position where the contact members engage with the commutating means.

17. In a rectifier commutating means, a polarized armature, contact members carried by the armature, electromagnets surrounding the armature and having pole pieces, in which one edge is cut away to produce an assymetrical field to cause the top of the axis of the armature to incline towards the rolling direction of the armature, conductors supplying multi-phase current to the magnets, and means for guiding the armature during the starting period to cause the armature to move in a helical path to the position where the contact members engage with the commutating means.

ERNST ALBERT EMANUEL TORNBLOM. 

